Method and device for handling telephone calls directed to non-reachable mobile phones

ABSTRACT

A method for handling telephone calls directed to a non-reachable mobile phone, and for handling data pertaining to them, wherein: I—provided the call diversion service to a different number, or the answering service, have not been enabled, the phone call is routed towards a phone call data management and storage device, when the mobile phone called user is non-reachable, dut to the fact that is in the detach mode or is temporarily out of the range reachable by radio-frequency signals; II—at the time mobile phone is again reachable, a notification is transmitted to the subscriber number of the telephone call; the notification being effected in the form of SMS, which contain phone call data of missed phone calls performed during the period while the mobile phone was not reachable.

FIELD OF THE INVENTION

The present invention generally refers to the problem of establishing acommunication with a subscriber in a cellular radio mobile network, andmore particularly it relates to a telecommunication service through acellular radio mobile network, which allows a subscriber to acquire thetelephone number of the subscriber who tried to call him while he wasnot reachable due to radio signalling absence, or because the mobilephone was in the detach mode. The invention is concerned both with themethod for implementing this service and with the functions of specialdevices employed when providing the same.

BACKGROUND ART

Recent estimates suggest that for every telephone network dealer, who atpresent is concerned with the public radio mobile service in Italy,there are daily tens of a million telephone calls which are unsuccessfulbecause the “target” mobile phone is not reachable or is in the detachmode.

In other words, notwithstanding the increased use of telephone answeringsystems (answering services), and call diversion services, itnevertheless happens, that in some special conditions, more than 400calls/second are missed, thereby limiting the extent of outgoing trafficor, in any case, providing a restricted or partially complete service tosubscribers.

The basic difficulty found by a network administrator when tackling thiskind of problem, is that of getting through a considerable traffic.

In fact, the problem of the recording and management—at the same time—ofsuch a noticeable amount of data due to the high number of unsuccessfulcalls, the difficulties caused by a consistent evaluation of thegeographical load of this service, the management of possible networkfailures, etc., have led to the situation that—up to now—a solution tothis problem has neither been considered nor put into practice.

This problem does not lend itself to a simple solution, since manyreasons may be the cause for the impossibility of establishing acommunication:

-   -   the radio mobile phone may be in the detach mode, the network        having acquired the signal which confirms this fact (detach);    -   the battery is discharged or is disconnected from its operative        position, or the SIM card is off;    -   a condition may exist wherein the transceiver station is not        reachable or not visible, as the radio channel is notoriously        very aleatory; etc.

At last, it would be necessary—in any case—to verify the possibleenabling of the call diversion service to the answering system or to afurther telephone number.

On the other hand, these conditions according to which it is impossibleto reach a called subscriber, have till now been accepted by the usersof the radio mobile service as intrinsically foreseeable but totallyinevitable. In other words, this problem relating to the impossibilityof establishing a connection has never been posed, because in comparisonwith the fixed network it was evident that the cellular telephonenetwork would necessarily lead to this drawback, due to the intrinsicnature of the principle of operation of a mobile phone, which couldmomentarily be non reachable or in the detach mode.

An object of the present invention is to provide handling procedures formanaging telephone calls directed to a radio mobile phone, which allowto improve the service, by eliminating the drawbacks due tocommunication barriers caused by the problem of a “non-reachable mobilephone”.

A further object of the present invention is to increase the number offree basic services offered to the users by the network dealer.

A last object of the present invention is to provide a method forhandling calls to a non-reachable radio mobile phone, and for handlingthe related, acquired information, the method employing standardprotocols, technologies and components in the field of cellular radiomobile phones, in order to permit easy maintenance and reduce the costof the method implementation.

DISCLOSURE OF INVENTION

These and further objects which will be apparent from the description,are obtained through a method for handling telephone calls directed to anon-reachable radio mobile phone and for handling information associatedto the calling subscriber (like telephone number, time of the telephonecall, and any additional information), wherein the method is started(triggered) by an event such as a vocal call, which in turn originates anotification through a recordable SMS text channel, and comprises thetwo distinct basic steps of:

I) routing the telephone call to a device for storage and management ofdata (information) relating to the phone call, when the calledsubscriber is not reachable, due to the subscriber mobile phone being inthe detach mode or due to the absence of a radio-frequency signal, andwhen, at the same time, the call diversion service towards the answeringservice or another phone number is not operative;II) transmitting, that is notifying, to the called subscriber, at themoment the mobile phone is reachable again, all SMS texts including datarelating to the calls missed in the period when the subscriber was notreachable;the method being based on a protocol, in which the usual steps sequencefor performing a mobile telephone network call, is first started andthereafter immediately interrupted after the signaling and acquisitionof the subscriber identification, and this steps sequence is resumed atthe time it has been ascertained that the cellular radio mobile phone isreachable again, but actuating this time an SMS text channel, so as tocompletely eliminate the actual serial operative step sequence(transaction) typical of a voice communication protocol, therebyproducing, in fact, a traffic having a virtual nature.

The method disclosed herein is basically different from the knowntelephone call diversion to the answering service, which involves in anycase a complete serial operative calling and answering step sequence(transaction) and therefore a cost for the user, which depends from thetime period during which the channel is engaged. The service has beenrealized using TACS, GSM, or GPRS technology, and it could also berealized by employing UMTS technology.

As far as the user is concerned, this service works according to thefollowing steps:

-   -   If a user is called while he is not reachable (cellular mobile        phone in detached mode, or absence of radio-frequency signal),        the calling user receives a vocal message informing him about        the fact that the called user cannot be reached (this service is        automatic, without any sort of control option being performed by        the calling user).    -   Immediately after the called user is reachable again, he        receives an SMS notification, including an indication of all        telephone calls missed during the period while he was not        reachable. The notification is sent by means of an SMS text to        the owners of a GSM radio mobile phone, and to the owners of        TACS radio mobile phones adapted to receive and transmit SMS        text messages, whereas the notification is sent in the form of        vocal SMS in case of TACS users whose cellular radio mobile        phone is not adapted to handle SMS text. The phone number of the        calling subscriber, the time of the telephone call, and any        other relevant information relating to the calling subscriber        and/or the called subscriber are transmitted at the same time.        In case a user (with the same phone number) has called several        times, only an indication pertaining to the most recent phone        call will be provided. Moreover, if the number of missed        telephone calls exceeds the available space in a single SMS,        further SMS will be sent. The information concerning missed        telephone calls may be stored only for a maximum predetermined        time period.

The service is not actuated in the following circumstances:

-   -   The call diversion service is already active, towards an        answering system or towards a different phone number;    -   The phone number of the calling user is not available or is not        presented (e.g. a phone call from abroad, or in case of a hidden        number, etc.)    -   The called user is roaming abroad.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the invention are described in the followingfor illustrative purposes only, without limiting the generality andpossible applications thereof, said embodiments being shown in theannexed figures, in which:

FIG. 1 is a schematic view of a network architecture, providing anindication of the method of operation of the present invention;

FIG. 2 is a block diagram of a fundamental procedure in the ambit of themethod according to the present invention;

FIG. 3 is a block diagram illustrating a further essential procedurerelating to the method of the present invention.

BEST MODES OF CARRYING OUT THE INVENTION

It is now useful, before starting with the detailed description, topreliminarily introduce a list of symbologies and abbreviations actuallyin use in the technical field to which the invention refers.

1. DETACH: the user has turned off his radio mobile cellular phone bypushing the “OFF” key.2. HLR Home Location Register: Database containing data relating toregistered cellular phones.3. IMSI: radio mobile identity of the SIM card.4. IP: network address defined in the Internet protocol.5. IAM Initial Address Message: Signaling message containing informationrelating to the calling/called person.6. ISUP ISDN User Part: GSM network signaling.7. MAP Mobil Application Part: it denotes (when MAP GSM is implied) theprotocol used by the nodes of the GSM network to manage the usersmobility.8. MSC mobile switching center: switching center for mobile telephony9. MSISDN Mobil Station Integrated Service Digital Network: it denotesthe number of the mobile phone (e.g. 0338 451845)10. PAGING: a radio signal diffused from the MSC/VLR to inform the radiomobile phone that a call has arrived.

11. PLMN: Public Land Mobile Network 12. PSTN: Public Switch TelephoneNetwork

13. ROAMING: denotes a condition wherein a GSM mobile phone happens tobe connected to a network which differs from the network which issuedthe GSM card of the mobile phone.14. SMS-C: service center for short messages15. STP Signaling Transfer Protocol: it denotes a function of thesignaling telephone network, which allows to transfer a signalingmessage to its destination, passing through intermediate nodes.16. TGDS TACS/GSM Gateway Delivery System: Multifunctional Hardware andSoftware Platform, implemented for integration of wireless messagesystems operative procedures.17. UCP Universal Computer Protocol: Protocol used in the datatransmission towards the service center SMS-C18. VLR Visitor Location Register: database containing informationrelating to the actual position of the mobile phone.

Referring now to FIG. 1, this figure schematically shows thearchitecture used for providing this service, with dotted linesindicating the functions of standard protocol stacks; on the other hand,FIGS. 2 and 3 denote the respective operative method used to carry outthis service, which includes the following steps:

I) the calling subscriber 1′, 1″ dials (step 30) the destination or“target” number and performs his telephone call by interconnectinghimself to a PSTN telephone network 4, in case the phone call iseffected from a fixed line 1′, or to the telephone network PLMN 5, incase the phone call is effected from a mobile phone 1″,II) the original switching center MSC 2 interrogates the subscribersregister 3 (hereafter HLR), at 31, by means of the STP 10, by asking theroaming destination number,III) the HLR 3 checks at 32 (based on the VLR number), if the mobilephone is roaming abroad (this step is valid only for the GSM network).

-   -   if the answer is “YES”, the phone call is handled according to        the usual procedure 33 provided for in GSM networks,    -   if the answer is “NO” the procedure continues through the steps        described below,        IV) the HLR 3 checks if the destination mobile phone is in the        DETACH mode (34):        IV i) if the answer is “NO”, it transmits (35) to the original        switching center MSC 2, the roaming number of the center MSC/VLR        in which the destination number is registered (destination        center) and the method continues as described below in steps V        and subsequent ones, which relate to checking if the mobile        phone is reachable;        IV ii) if the answer is “YES”, it is checked—at 36—if the        destination number has enabled the call diversion service        towards its own answering service or towards another phone        number:    -   if the answer is “YES”, the number towards which the call        diversion is active is returned (at 37) to the original exchange        2 (MSC), and the method proceeds by going back to step H;    -   if the answer is “NO”, the number of the device 9 for the        storage and management of phone calls (hereafter also called        “paging management”) is returned (at 38) to the original        exchange (MSC) 2, and then the method proceeds as described in        step VI.        V In case the preliminary check on the DETACH mode of the mobile        phone has led to a negative result, the destination center        performs a further test 40 in order to establish if the        destination (“target”) mobile phone is reachable:    -   if the answer is “YES”, the usual procedure for a phone call is        started at 33, following the common procedure provided for in        radio mobile phone systems.    -   if, on the other hand, the mobile phone is not reachable, a        connection is established at 38, towards the number of the        device 9 for the paging management, and the method proceeds        according to the following step.        VI) If the mobile phone is turned off or is not reachable, and        no call diversion is enabled, the calling user receives an        announcement and the phone call is routed towards the device 9        for the paging management.

In order to increase the degree of reliability the design is realized insuch a way as to use two nodes of paging management. Both nodes sharethe same Data Base 14 of the phone calls, which is duplicated in therespective sites. In order to manage correct synchronization andmanagement of the two Data Base systems, and in order to avoid accessconflicts on the same records (as would occur when two users call at thesame time the same person whose mobile phone is turned off or notreachable by a radio-frequency signal), it was decided to define twoseries of different numbering on the HLR 3 for call-forwarding to thepaging management device (these series are called “Call Forward NumberMSISDN Paging_(—)1” and “Call Forward Number MSISDN Paging_(—)2”). Thetotal number of numberings will be 10 (in order to leave a margin forpossible future introductions of other paging management platforms), andthey are formed by adding at the end of the numbering “47000”, the lastnumber of the MSISDN of the called user with respect to whom the serviceis made active. To this purpose, the paging management device 9,—that isthe device for the storage and management of information relating tophone calls towards a non-reachable mobile phone—, satisfies a pluralityof specific functional requirements which relate to the ability ofcooperating, through the management of the protocol ISUP, with theswitching nodes of the GSM network, and to the ability of extracting thecalling number from the ISUP LAM message for the phone calls directed toa non-reachable mobile phone or in case of absence of a radio-frequencysignal; furthermore there is provided the possibility of storing in adedicated Data Base 14, all information related to phone calls directedto each mobile phone not reachable due to absence of radio frequencysignal.

Moreover, the paging management device 9 is suited to cooperate with theHLR, through the management of the MAP protocol, for a switching requestwith regard to the return of momentarily non reachable mobile phones,inside the area reachable by radio-frequency signals. At last, it isalso capable of interfacing itself,—through the management of the UCPprotocol—, with the SMS service center 11 of the GSM switching center,in order to send text messages towards the mobile phones which havereturned inside the area where radio-frequency signals are active.

On the other hand, under the aspect of the procedural realization ofspecific functions according to the present invention, the pagingmanagement device 9 successively performs the following operations:

I—It receives, at 50, only the signaling component of the phone call, itextracts the number of the calling subscriber from the LAM message ofthe ISUP signaling, it records the hour/date of the telephone call (withan accuracy of one second), and then it emits an appropriate delivermessage (at 51) with respect to the MSC/VRL which is sending the data.This allows the MSC/VLR to possibly send a courtesy message (at 52), tothe calling user, to deliver the phone call so as to release the phonicchannel;II—it activates a check at 53, in order to determine whether the callingnumber is already in the list of numbers that already tried to reachthis particular subscriber; depending on the result of this check, itperforms the following operations:

-   -   provided this number is already in the list of calling numbers        for that subscriber, it replaces (at 54) the hour/date of the        last phone call performed by this user number, with the        hour/date recorded during the preceding step;    -   if, on the other hand, this number is not in the list of calling        numbers for that subscriber, it adds this number to the list (at        55), together with an indication of the hour/date of the last        telephone call;        III—if from a test 56, it follows that the phone call        corresponds to a first phone call, directed to the called        subscriber during the period when he was not reachable, a        request is made (at 57) to the HLR 3 (through MAP SET MESSAGE        WAITING DATA) to receive a notification immediately after the        “target user”, that is the subscriber, is again reachable.

When the addressee of the telephone call is again reachable, the HLR 3communicates this fact to the paging management device 9. According to apreferred embodiment of the present invention, once the notification hasbeen received, the paging management device subdivides the number listassociated to the target mobile phone, into groups of four elementseach, and for each of said groups it defines a text message to be sentto the user, containing information related to the phone calls comprisedin this group.

The paging management device sends to the short message service center,11, the above defined messages, through the UCP protocol, indicating asaddressee the number of the destination (that is, target) mobile phone.

Finally, the SMS-C sends the messages to the destination mobile phone atthe time it is reachable again.

The system that realizes the network architecture according to the abovedescription is suited to provide a very high capacity of trafficmanagement: it is able to manage 350 phone calls per second, and up to10 millions phone calls per day. These performances are obtained througha logical subdivision of the network load on a plurality of nodes andthrough the use of technologies, which are partly already known andalready used in the field of telephony, but which are combined by meansof the necessary implementations, extensions and modifications, so as tobe able to finally provide the users with a new free service.

This service is already (default) enabled, although the user may requestits deactivation by calling and dialing a new special option of a voicemenu; subsequently, he can also request reactivation of this service, byperforming similar actions.

1. (canceled)
 2. A method for handling a telephone call from a callingsubscriber to a radio mobile phone of a called subscriber, the telephonecall comprising a signaling component and a phonic channel, the methodcomprising the steps of: I—determining if the called subscriber is notreachable, due to the mobile phone being in detach mode or due toabsence of a radio frequency signal, and if a call diversion devicetowards an answering service or another phone number is not operative;II—in the affirmative case, routing only the signaling component of thetelephone call from a switching node to a device, distinct from theswitching node, for storage and management of data relating to thetelephone call; III—at said storage and management device, extractingthe telephone number of the calling subscriber from the routed signalingcomponent of the telephone call, and recording in a number list saidtelephone number and the hour/date of the telephone call; IV—emitting adeliver message from said storage and management device to saidswitching node, in order to allow said switching node to release thephonic channel of the telephone call; V—determining, at said storage andmanagement device, if the mobile phone of the called subscriber isreachable again; VI—in the affirmative case, sending a messagecomprising said telephone number and said hour/date-of the telephonecall, from said storage and management device to a SMS service center;VII—transmitting from said SMS service center to the mobile phone of thecalled subscriber, a SMS message including said telephone number andsaid hour/date of the telephone call.
 3. The method for handling atelephone call according to claim 2, characterized in that the recordingin step III further comprises: checking whether the telephone number ofthe calling subscriber is already included in said number list togetherwith hour/date of a previous telephone call; in the affirmative case,replacing, in the number list, the hour/date of said previous telephonecall performed by said calling subscriber, with the hour/date of thetelephone call; in the negative case, adding the telephone number of thecalling subscriber and the hour/date of the telephone call to saidnumber list.
 4. A mobile network comprising a HLR, a SMS center, aplurality of switching nodes and a device, distinct from the switchingnodes, for the storage and management of data relating to a telephonecall directed to a called mobile phone, when the latter is in the detachmode, or when a radio-frequency signal cannot reach said mobile phone,and when a call diversion device towards an answering service or anotherphone number is not operative, wherein the storage and management deviceis configured to: cooperate with the switching nodes of the mobilenetwork, and extract the telephone number of a calling subscriber from asignaling component of said telephone call, store and handle saidextracted telephone number and the hour/date of the telephone call;cooperate with the HLR of the mobile network, for performing a requestof notification of a return of the called mobile phone within an areareachable by radio frequency signals; cooperate with the SMS center ofthe mobile network, in order to send a SMS message to said called mobilephone returned within an area reachable by radio-frequency signals, saidSMS message including said extracted telephone number and said hour/dateof the telephone call.
 5. A mobile network according to claim 4, whereinthe telephone call comprises a signaling component and a phonic channel,and the storage and management device is configured to receive from theswitching nodes of the mobile network only the signaling component ofthe telephone call and extract the telephone number of the callingsubscriber from the received signaling component of the telephone call.